1. Field of the Invention
The present invention relates to a process for producing protein products on the basis of bone-containing animal material, characterized in what is stated in the characterizing part of claim 1.
2. Description of the Related Art
Hog and cattle slaughterhouse waste is usually processed in meat processing plants to industrial lard and meat-and-bone meal used for protein supplement for animal fodder.
Danish patent specification No. 147 568 thus describes a process for scouring and dewatering animal waste essentially comprising slaughterhouse waste, confiscates and dead beasts. According to this process the waste is comminuted into pieces, the diameters of which essentially do not exceed 20 mm, and the comminuted material is heated to a temperature within the range 40.degree.-60.degree. C. Considerable amounts of glue-water and liquid fat are removed from the said material in a screw press. The resulting press cake containing bone and meat protein may subsequently be dried, sterilized and ground to a fine powder suited for fodder supplement. It contains about 45% protein, which corresponds to the protein-content of ordinary meat-and-bone meal.
For many uses the bone material in the product is only an useless filler, as the meat-and-bone meal is primarily dosed according to its meat protein content. However, the bone material has a high content of calcium phosphate, and as it is also desirable to obtain a protein product having the highest possible protein content, the press cake may advantageously be separated into a protein-containing meat fraction and a mineral-containing bone fraction.
Thus, it is the object of the present invention to devise a process for producing protein products from bone-containing animal material, by which process the bone material can be separated from the meat protein material in a commerically useful way. According to the present invention it has surprisingly been found that it is possible in an efficient way to separate a bone-containing animal material into two fractions, viz. a meat fraction rich in protein and a mineral-containing bone fraction, each separately being commercially interesting.
It is known to separate a bone-containing material into several commercially interesting fractions. EP patent specification No. 0 020 722 thus describes a process for continuously producing gelatine from a meat and fat-containing bone material which is chopped and separated into a meat/fat fraction and a bone fraction. The bone fraction is ground and heated to maximally 121.degree. C., and after air classification a material is obtained which is usable for producing gelatine.
U.S. Pat. No. 3,594,190 describes a process for recovering adhering meat from bone waste. The waste is tumbled in a rotating drum in the presence of water or salt brine, whereby a meat slurry is formed which due to its binding power and food value can be used in sausage manufacture.
DK public disclosure No. 146 872 describes a process for producing fat and meat-and-bone meal from animal raw materials, by which slaughterhouse waste is boiled and centrifuged, the solid components subsequently being dried to a meat-and-bone meal having a protein content of about 40%. The liquid phase is separated into fat, glue-water and slurry in a centrifuge. The glue-water is concentrated and dried together with the slurry to form a second meat-and-bone meal fraction having a protein content amounting to 66%.
DK public disclosures No. 150 005 and 150 006 describe production of protein products from animal raw materials. According to the former disclosure slaughterhouse waste is pressure boiled and subsequently separated into solid matter and liquid. The solid matter is dried and separated by means of a sieve into meat-and-bone meal containing about 46% protein and a bone product which is ground to a mineral powder containing about 30% protein, while the liquid is separated into fat and glue-water which is spray-dried to form a glue powder containing about 79% protein. The latter disclosure describes a heat treatment at 80.degree.-100.degree. C. in water of slaughterhouse waste containing entire bones and/or large bone pieces. When meat tissue and fat tissue by the treatment have been loosened from the bone material it is removed from the slurry by means of a sieve and processed into a glue powder rich in protein, while the slurry after separation from fat and glue-water can be dried to a meat protein powder having a protein content above 70%.